The best dairy product (5)
I believe the answer is:
cream
This clue is a double definition.
'the best' is the first definition.
(as in 'the cream of the crop')
'dairy product' is the second definition.
(I know that cream is a type of dairy product)
(Other definitions for cream that I've seen before include "treat for cat?" , "Elite; colour" , "Beat" , "Top of milk or society" , "Pick - fatty part of milk" .)